The present disclosure generally relates to methods of forming contacts to a photovoltaic device, and particularly to non-lithographic methods of forming contacts to a front surface of a photovoltaic device on which light impinges.
Many photovoltaic devices employ a semiconductor p-n junction to induce spatial asymmetry by which electron-hole pairs generated by photons are directed in different directions. Typically, one type of semiconductor material is present on one side of a photovoltaic device, and the opposite type of semiconductor material is present on the other side of the photovoltaic device. The p-type material can be present on the front side and the n-type material can be present on the back side, or vice versa.
Light that impinges onto a front surface of a photovoltaic device passes through the front surface and generates an electron-hole pair within the semiconductor material. An electrostatic field generated by the p-n junction causes the electrons generated by the light to move toward the n-type material, and the holes generated by the light to move toward the p-type material. Contacts are made to the front side and the back side of the photovoltaic device to collect the charge carriers, thereby providing electromotive force for the photovoltaic device.
Contacts to the back surface of a photovoltaic device do not need patterning because light does not need pass through the back surface. Thus, a conductive sheet is typically employed as a back side electrode. Contacts to the front surface of a photovoltaic device need to be made to maximize the transmission of light through the front surface. Thus, contacts to the front surface of a photovoltaic cell are patterned, typically as a conductive grid having a pattern of parallel lines that are tied at one side or at both sides of the grid.
While such a conductive grid can be patterned employing lithographic methods, such processing steps tend to be expensive and time consuming. Thus, inexpensive and fast processing methods for forming contact structures on a front surface of a photovoltaic device are desired.